CVE-2026-77905: Windows WMI Use After Free Vulnerability

CVE-2026-77905 Overview

CVE-2026-77905 is a use-after-free vulnerability [CWE-416] in Windows Management Instrumentation (WMI). An authorized local attacker can exploit the flaw to elevate privileges on an affected Windows system. Microsoft disclosed the issue through its Security Update Guide, and it carries a local attack vector with high attack complexity.

Successful exploitation grants high impact to confidentiality, integrity, and availability. The vulnerability requires low privileges and no user interaction, but the high attack complexity reflects the timing conditions inherent in freeing and reusing memory in the WMI subsystem.

Critical Impact
A local, authenticated attacker who wins the required race can escalate to SYSTEM-level privileges through the WMI service.

Affected Products

Microsoft Windows (Windows Management Instrumentation component)
Refer to the Microsoft Security Update Guide for the full list of affected Windows builds
Server and client SKUs shipping the vulnerable WMI service

Discovery Timeline

2026-09-08 - CVE-2026-77905 published to NVD
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-77905

Vulnerability Analysis

The vulnerability resides in the Windows Management Instrumentation service, a core Windows subsystem used for local and remote management operations. WMI runs with SYSTEM privileges and processes requests from lower-privileged callers. A use-after-free condition in this code path allows an attacker who can invoke WMI operations to influence memory that has already been released.

When the freed object is reused by the service, an attacker who has reclaimed the underlying allocation can control function pointers, virtual method tables, or other referenced data. That control converts a memory-safety bug into arbitrary code execution inside the WMI service context. The result is a privilege escalation from a standard authenticated user to SYSTEM.

The local attack vector and low-privilege requirement mean the flaw is useful as a post-compromise step. Adversaries who obtain initial access through phishing, stolen credentials, or a browser exploit can chain this issue to gain full control of the host.

Root Cause

The root cause is a use-after-free [CWE-416] in a WMI object lifetime path. Object reference counting or cleanup ordering releases memory while another code path still holds a pointer to it. Subsequent dereference of that stale pointer operates on attacker-influenced data.

Attack Vector

Exploitation requires local access and valid credentials on the target system. The attacker invokes WMI operations that trigger the vulnerable allocation and free sequence, then races to place controlled data into the reclaimed allocation before the stale reference is dereferenced. Microsoft has not published exploitation details. See the Microsoft Security Update Guide entry for CVE-2026-77905 for authoritative technical information.

Detection Methods for CVE-2026-77905

Indicators of Compromise

Unexpected crashes or restarts of the WinMgmt service or wmiprvse.exe processes
WMI provider host processes spawning unusual child processes such as cmd.exe, powershell.exe, or rundll32.exe
New services, scheduled tasks, or accounts created shortly after WMI service anomalies
Local user sessions issuing high volumes of WMI queries or method invocations against sensitive namespaces

Detection Strategies

Monitor Windows Event Log channels Microsoft-Windows-WMI-Activity/Operational and Application for error entries referencing WmiPrvSE or access violations
Alert on process ancestry where wmiprvse.exe or svchost.exe hosting WMI launches interactive shells or LOLBins
Correlate WMI activity with sudden privilege changes, token elevation events, or SYSTEM-context process creation from non-administrative users

Monitoring Recommendations

Enable command-line auditing (Event ID 4688) and PowerShell script block logging to capture WMI-based tradecraft
Forward WMI activity and process creation telemetry to a centralized data lake for retention and correlation
Baseline normal WMI usage per host role so that anomalous invocation patterns from standard user accounts stand out

How to Mitigate CVE-2026-77905

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-77905 to all affected Windows systems
Prioritize patching on multi-user hosts, jump servers, and systems accessible to standard users
Audit local account membership and remove unnecessary interactive logon rights to reduce the pool of potential attackers

Patch Information

Microsoft addressed the vulnerability through its Security Update Guide. Administrators should consult the Microsoft advisory for the specific KB articles, cumulative updates, and build numbers that remediate CVE-2026-77905 across supported Windows versions.

Workarounds

No official workaround has been published; patching is the primary remediation path
Restrict local logon and remote WMI access to trusted administrators where feasible
Enable attack surface reduction rules that block untrusted processes from creating child processes via WMI
Increase logging and endpoint monitoring on hosts that cannot be patched immediately

bash

# Verify WMI service status and recent patch level on Windows
Get-Service Winmgmt
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10